Emergency lighting, sometimes referred to as egress lighting, is lighting that is activated in the event of power loss. One purpose of emergency lighting is to allow occupants of a building to safely exit the building in the event of a power outage or other emergency. Emergency lighting is mandated for use in commercial buildings by many electrical codes. Such codes generally specify the amount of light that must be provided in the event of power loss and the duration of time for which such light must be provided. For example, U.S. building codes require emergency lighting to provide one footcandle of light for a minimum of 90 minutes along the path of egress during a power outage.
In buildings, emergency lighting is commonly provided by battery-powered emergency light fixtures that are installed in a building along with the luminaires that provide light in non-emergency situations. Existing fluorescent emergency lighting systems can be configured so that the emergency ballast 12 serves the function of both providing regular illumination and emergency lighting without the need for a separate lamp ballast. Other luminaires may be used for emergency lighting, but they are limited and cannot account for differences in emergency driver specifications.